Medications that are available on the veterinary market for treating infections, particularly in fish, are chemicals like formaldehyde or malachite green. Although efficient, these chemicals have the disadvantage of providing undesirable or toxic side effects. The mode of administration is also not ideal. The injured fish may be soaked in a medicated bath unnecessarily for a topical injury and, this may be even undesirable because of its systemic effects (the fish ingests the medication when a topical effect is sought). Alternatively, a local application can be made: the fish is netted, positioned and localized lesions are quickly sprayed with the chemical mixture. The fish is usually rinsed off in a container of water before being returned to a tank or to its aquarium. The objective is to keep the contact time of the fish with the chemical mixture as short as possible to avoid necrosis or burns. Some antibiotics and steroids administered that way may be efficient although their contact time with the skin is relatively short. Another drawback of the topical application as it now exists is that there is a loss of medication which goes into the rinsing water and that is not used for the treatment per se. There is certainly a need to improve and to maximize the contact time of a medication with minimal loss and toxicity.
A first type of skin adhesive gel has been described in EP 625, 034. These gels are water-insoluble but water-swellable cross-linked ampholyte salts of PVP and amines. These hydrogels may be coated with a urethane film backing to control the moisture vapour transmission rate. There is no disclosure of an urethane gel itself serving as an adhesive drug-releasing matrix further having the property of being water-dispersible.
Another type of protective gel is disclosed in U.S. Pat. No. 5,019,604. This gel is intended to be used for covering surgeons' hands together with standard surgical gloves. The gel is mainly composed of lanolin, silicone, a surfactant and polytetrafluorethylene powder used as a water repellent. The gel is removable with alcohol and surfactants, and thus does not appear to be water dispersible. For treating fishes, water dispersibility is necessary for recovery of a healthy state.
Furthermore, the treatment of infectious diseases, specifically in fishes, would benefit from finding any new compound, preferably of a natural origin, which would be innocuous.
Combining an efficient and safe compound with a new delivery matrix would further reduce the need for quarantines and would minimally affect the quality of the water environment.